Conventionally, in order to automate the cleaning of the main body of a toilet following usage, a human detection sensor such as an infrared sensor is installed in the toilet stool, and if the human detection sensor detects a user for a fixed period of time or more, the sensor then detects the departure of the user and flushes the toilet stool with a fixed quantity of cleaning water. However, in such automatic cleaning systems based on human detection, the toilet stool is flushed with a fixed quantity of cleaning water regardless of whether the toilet stool has been used or the quantity of urine, leading to a great deal of waste.
A device for solving this problem, proposed in Japanese Patent Unexamined Publication No. H10-37284, detects variation in the water pressure at the trap portion of a toilet stool using a pressure sensor, and thereby detects variation in the water level of the trap portion, or in other words urination. According to this system, the fact that urination has occurred is detected, and hence cleaning water is not supplied mistakenly when a person stands before the toilet stool but does not urinate. Moreover, the quantity of urine that was passed is detected and cleaning water is supplied in accordance with the quantity of urine, and hence wasteful flushing using an unnecessarily large quantity of cleaning water does not occur.
Further, if cleaning water continues to be flushed into the toilet stool when the drain pipe is blocked, the water level rises such that the cleaning water overflows from the toilet stool, but by detecting the water level, a valve is controlled in advance such that an overflow of cleaning water from the main body of the toilet stool can be forestalled.
Also, the supply condition of the cleaning water can be detected by the pressure sensor, and hence warnings can be issued upon the detection of a “stoppage” or “leakage”.
However, this cleaning system using a pressure sensor is constituted such that the trap portion and pressure sensor are connected by piping in order to detect the water pressure inside the trap, and hence water tightness must be secured in the piping connection portion at the trap portion over a long period of time. However, in reality this is not easy. Moreover, a protective member is required for preventing the infiltration of liquid or harmful gas into the sensor portion, making assembly difficult. To prevent the water pressure-detecting piping portion from blocking, a portion of the cleaning water is supplied to clean the piping, but this leads to an even more complex constitution, making assembly difficult and becoming a possible cause of breakdowns. Moreover, when a breakdown occurs in the piping portion, repairs from the back portion of the toilet stool can proceed only when the toilet stool is separated from the water supply pipe and drain pipe and moved away from the wall surface, and hence this system is highly unrealistic.
The basic issue in detecting the water pressure at the trap portion is the influence on pressure variation in the drain pipe. More specifically, in general a drain pipe is connected to the drainage portions of a plurality of instruments such as toilet stools and wash basins, whereby the drainage from each individual instrument is collected and transmitted to a sewerage facility. The pressure inside the drainpipe varies constantly depending on the drainage from the plurality of instruments, and the water pressure inside the trap of the toilet stool varies in accordance therewith. Hence in reality, it is difficult to detect only urine reliably.